Saturn and its rings are a continuously-playing show of beauty and grace, but the giant planet also has a vast retinue of moons, each as different from each other as any family of siblings (which make it very hard to pick my favorite from ones like this or this). The biggest, the aptly-named Titan, is a monster, bigger than the planet Mercury and possessing an atmosphere of nitrogen that's twice as thick as Earth's! The atmosphere is so thick and opaque that it blocks our view of the ground in visible light. Infrared light can penetrate that gloom, though, and it's not by coincidence that the Cassini spacecraft is equipped with filters and detectors designed to look in those wavelengths.

Using that equipment, astronomers created the first-ever multicolor map of the surface of Titan (a map using a single color was created in 2009). This false-color map shows elevated regions (white areas), lakes of liquid methane and ethane near the north pole of the moon, and what's most amazing to me, vast areas of wind-blown dunes (shown in brown)! Those aren't grains of sand in the dunes, but grains of frozen hydrocarbons, blown across the plains by Titan's thick air. Detailed radar observations by Cassini show them to be much like dunes on Earth, but a bit chillier: the temperature on the surface of Titan is a numbing (or perhaps I should say "shattering") -180°C (-300°F).

And yet, it's a world not so different than ours: atmosphere, liquid lakes, wind... and at those temperatures, the chemistry of methane is similar to that of water at room temperature on Earth. It's not crazy to wonder if there's life on Titan...